Organisms cope with the oxidative stress of an oxygen environment by synthesizing antioxidant enzymes. These enzymes are usually 20,000 to 100,000 molecular weight and have either transition metals or heme as catalytic components. Superoxide dismutases scavenge the superoxide radical and protect the cell from the deleterious effects of that radical. A novel superoxide dismutase activity has recently been found in extracts of heart and lung tissue. The activity, named ersatz SOD, is associated with a heat stable, low molecular weight ligand specific for Cu or Mn. The general goal of the research is to characterize the ligand components both physically and chemically. The component(s) will be isolated to homogeneity by ultrafiltration, gel exclusion and ion exchange chromatography. Optimal conditions for assay of the catalytic activity both spectrophotometrically and histochemically will be developed. Composition of the ersatz SOD will be determined by amino acid analysis and Fast Atom Bombardment Mass Spectrometry. The uv-visible and electron paramagnetic resonance spectra of the hololigand and metalloligand complex will be measured. Location of the ligand within heart and lung tissue will be found with immunocytochemical techniques. There is the potential for use of the SOD mimic as a therapeutic or anaphalytic agent during medically imposed ischemia - reperfusion and as a possible radioprotectant during radiation therapy.